exec

The exec function executes a system command and never returns--
use system instead of exec if you want it to return. It fails and
returns false only if the command does not exist and it is executed
directly instead of via your system's command shell (see below).

Since it's a common mistake to use exec instead of system, Perl
warns you if there is a following statement which isn't die, warn,
or exit (if -w
is set - but you always do that). If you
really want to follow an exec with some other statement, you
can use one of these styles to avoid the warning:

If there is more than one argument in LIST, or if LIST is an array
with more than one value, calls execvp(3) with the arguments in LIST.
If there is only one scalar argument or an array with one element in it,
the argument is checked for shell metacharacters, and if there are any,
the entire argument is passed to the system's command shell for parsing
(this is /bin/sh -c on Unix platforms, but varies on other platforms).
If there are no shell metacharacters in the argument, it is split into
words and passed directly to execvp
, which is more efficient.
Examples:

If you don't really want to execute the first argument, but want to lie
to the program you are executing about its own name, you can specify
the program you actually want to run as an "indirect object" (without a
comma) in front of the LIST. (This always forces interpretation of the
LIST as a multivalued list, even if there is only a single scalar in
the list.) Example:

When the arguments get executed via the system shell, results will
be subject to its quirks and capabilities. See `STRING` in perlop
for details.

Using an indirect object with exec or system is also more
secure. This usage (which also works fine with system()) forces
interpretation of the arguments as a multivalued list, even if the
list had just one argument. That way you're safe from the shell
expanding wildcards or splitting up words with whitespace in them.

The first version, the one without the indirect object, ran the echo
program, passing it "surprise"
an argument. The second version
didn't--it tried to run a program literally called "echo surprise",
didn't find it, and set $?
to a non-zero value indicating failure.

Beginning with v5.6.0, Perl will attempt to flush all files opened for
output before the exec, but this may not be supported on some platforms
(see perlport). To be safe, you may need to set $|
($AUTOFLUSH
in English) or call the autoflush()
method of IO::Handle
on any
open handles in order to avoid lost output.

Note that exec will not call your END
blocks, nor will it call
any DESTROY
methods in your objects.

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